The anatomical perspective of human occipital condyle in relation to the hypoglossal canal, condylar canal, and jugular foramen and its surgical significance

Abstract

Background: The transcondylar approach (TCA) has gained importance in recent era which enables shorter and direct route to access the lesions ventral to the brainstem. The important step in this approach is resection of the occipital condyle (OC). The detailed knowledge of bony anatomy of OC and its relation to the hypoglossal canal (HC), condylar canal (CC), and jugular foramen (JF) is very important to avoid any iatrogenic injury during craniovertebral surgeries. The aim of the present study is to conduct a morphometric and morphological study and note the variations of the OC and the structures surrounding it in North Indian population.

Materials and methods: The study was carried out on 100 OC. Morphometric measurements of OC and the distances of HC and JF from the posterior end of OC were noted. In addition, the extent of the HC and JF in relation to OC, presence or absence of CC, shape of the OC, and its articular facet were also noted.

Results: The incidence of short OC was seen in 13% skulls. The most common shape of OC was oval or rhomboid. Even though the articular facet was convex in majority of skulls but flat (10%) and concave (1%) were also observed. The external and internal distance of HC from the posterior end of OC was13.83 mm and 10.66 mm on the right side and 15.02 mm and 11.89 mm on the left side. The OC was related in its middle 1/3 to the HC in 15% skulls and to the whole extent of JF in 3% skulls. Thirty-four percent skulls displayed the septa in the HC. The CC was present bilaterally in 38% skulls and unilaterally in 40% skulls.

Conclusion: The OC and related structures such as HC, CC, and JF are likely to have variations in respect to morphometry and morphology. This study may prove helpful to neurosurgeons operating in this field, especially during TCA where neurovascular structures emerging from these canals and foramen are more vulnerable to injury.

Keywords: Condylar canal; hypoglossal canal; jugular foramen; occipital condyle; transcondylar approach.

Figure 1

Foramina present in relation to occipital condyle: red-hypoglossal canal, black-jugular foramen, blue-condylar canal

Figure 2

Morphometric measurements of occipital condyle: 1-length of occipital condyle, 2-width of occipital condyle, 3-thickness of occipital condyle, 4-anterior intercondylar distance, 5-posterior intercondylar distance

Figure 3

Morphometric measurements around hypoglossal canal and jugular foramen: (Left side) 1-distance of posterior end of occipital condyle from the posterior margin of jugular foramen, 2-distance of posterior end of occipital condyle from external opening of hypoglossal canal, 3-distance of posterior end of occipital condyle from the internal opening of hypoglossal canal. (Right side) a1/3-anterior one-third of occipital condyle, m1/3-middle one-third of occipital condyle, p1/3-posterior one-third of occipital condyle

Figure 4

Shape of the occipital condyle: 1-circular, 2-oval, 3-rhomboid, 4-S shape, 5-reniform, 6-triangular, 7-quadrangular, 8-pentagonal, 9-comma shape, 10-irregular

Figure 5

Shape of the facet of occipital condyle: 1-concave, 2-flat, 3-convex+, 4-convex+++

Figure 6

Condylar canal: 1-bilaterally present, 2-unilaterally present, 3a-condylar canal (black arrow) opening anteriorly lateral to hypoglossal canal (yellow arrow), 3b-condylar canal (black arrow) opening anteriorly in the posterior boundary of jugular foramen (yellow arrow)